mysql - 如何在两个选择之间在mysql中使用算术减号？

Question

select player.ActionTime from question_log log inner join player_question player 
where log.ActionType='96'

select player.ActionTime from question_log log inner join player_question player 
where log.ActionType='97'

如何在 mysql 语法中实现这一点？选择 ActionType 为 96 减去另一个为 97 的 Actiontime。算术减。

Answer 1

SELECT t96.ActionTime - t97.ActionTime
FROM
(
    select player.ActionTime 
    from question_log log 
    inner join player_question player 
    where log.ActionType='96'
) t96
CROSS JOIN
(
    select player.ActionTime 
    from question_log log 
    inner join player_question player 
    where log.ActionType='97'
) t97

请注意，您的两个查询之间似乎没有任何关系，所以我只能建议一个CROSS JOIN（笛卡尔积）。如果你有不止一行 log.ActionType = '96' 或 log.ActionType = '97' 你将有很多结果行。

Answer 2

使用子查询：

SELECT player.ActionTime - (SELECT player.ActionTime from question_log log inner join     player_question player where log.ActionType='97' LIMIT 1)
from question_log log inner join player_question player where log.ActionType='96'